Can You Have a Gas Stove in Your ADU in Massachusetts?

By Buz Artiano, BuildX | May 2026

Watch: The Good, The Bad & The Ugly Truth About Energy Ratings w/ Andrew Popielarski | BuildX Podcast #04

If you've been looking into ADUs in Massachusetts, you've probably heard the crazy warnings that everything has to be all-electric now. As in no gas stoves, no propane, nothing but electric, no exceptions. For people who love to cook with a gas stove and really don't want to give that up, it kinda feels that's a dealbreaker on the whole project. We understand why you feel that way, and it's a common thing that people worry about when they're thinking about building an ADU.

My name is Buz Artiano, I'm the founder and CEO of BuildX, we've built countless ADUs in Massachusetts, but most of our builds have been around the South Shore and Plymouth County. We do all the design, permitting, and construction ourselves, and we are very familiar with the state's energy code, septic constraints, and zoning requirements. When the Department of Energy Resources changed the ADU energy rating rules in February 2025, we were one of the first builders in the state to understand what it meant for our clients and how it would affect the whole gas stove issue.

Basically, yes, you can have a gas stove in a Massachusetts ADU. The things that really matter are how it can affect your energy rating, cost to build, and your overall design. In this article we are going to break all this down so you can make the right decision before you start talking to builders.

Is Gas Allowed in a Massachusetts ADU?

Yes. As of February 14, 2025, the Massachusetts Department of Energy Resources announced that ADUs would be in their own category when it comes to the state energy code. Before that, ADUs had to get the same energy ratings as full-size homes, which was a 45 for all-electric homes and a 42 for mixed-fuel homes. To get those scores, the house had to be extremely tightly sealed and have expensive insulation, so a lot of times builders gravitated toward all-electric designs just because it was easier to get the score that's required.

The new ADU-specific ratings are HERS 55 for all-electric and HERS 52 for mixed fuel. HERS stands for Home Energy Rating System score, on this scale the lower the number, the more efficient the home is. The difference between 55 and 52 is actually significant when it comes to how you approach the construction, but both numbers are achievable without having to take the extreme measures that a score of 42 would require. That one little change in the code reopened the door to gas stoves, propane cooking, gas hot water, and gas heating for ADUs.

The code still falls under the IECC 2021 with Massachusetts amendments. ADUs did not get a separate building code. They got a separate energy score requirement. You can review the full ADU requirements at mass.gov.

What Does "Mixed Fuel" Actually Mean for Your ADU?

Mixed fuel means your ADU uses any combination of gas, propane, or oil in addition to the electric systems. Most of the appliances that use any kind of mixed fuels are for heating, hot water, and cooking. If any of those three systems run on gas or propane, your ADU is classified as mixed fuel and it has to get a score of 52, but if it were all electric, it would only need to score a 55.

There are a few exclusions that are important to remember. One is a propane fireplace, a fireplace doesn't count as a mixed fuel system. A backup generator is also not included in that, and neither is any outdoor appliances that run on propane, such as a grill. The mixed-fuel classification only applies to the three main systems, which are heating, hot water, and cooking.

This means you could build an all-electric ADU with a heat pump, an electric water heater, and an induction cooktop, get your 55 energy score, and still install a propane fireplace and an outdoor gas grill without it affecting anything. Or you could install a gas stove, keep your heating and hot water electric, and get to that 52 score. The point is, you've got options.

What Is the Difference Between HERS 52 and HERS 55 in Construction?

The three-point gap between 52 (mixed fuel) and 55 (all-electric) isn't as small as it seems. It changes how you have to do the insulation, it changes your blower door results, and also what kind of windows you install. To get that lower score means you have to have a tighter, more efficient building envelope.

To get to 55 (all-electric), you usually need about 3 air changes per hour on a blower door test. You can get to that number with standard closed-cell foam insulation and good quality construction. You shouldn't need anything expensive or difficult for that.

To get to 52 (mixed fuel), the building needs to be sealed very tightly. The insulation may need to work harder because it will have to account for the gas appliances being less efficient than electric, so it has to pick up that slack. That usually means adding extra insulation in the walls or ceiling, paying very close attention to sealing every tiny gap or crack, and picking windows that are very energy efficient. The difference isn't dramatic, but it's definitely there, and it will affect your construction budget.

We evaluate everything related to energy options and requirements for every ADU before we give a price. In our experience, the price difference between building an ADU with a 55 energy score and one with a 52 depends mostly on the windows and the insulation. On some projects, it's not a huge difference because the building was already sealed tight enough. On others, in order to get to that 52, it requires upgrading all the windows to a high-solar-heat-gain glass, like Anderson's passive sun windows, which can raise the energy score without having to up to triple-glazed windows. That alone can save thousands of dollars on window orders and still get you to that score you need to have mixed fuel appliances. We involve the person we know that does the HERS ratings before we do any window purchases for exactly this reason. Once you're locked into a window type, that in turn affects decisions on insulation, wall assembly, and blower door tests. Getting the energy strategy right before ordering materials is one of the most important things you can do on any ADU project.

Could You Always Use Gas, Even Before the Code Change?

Technically, yes. Even under the previous score requirement of 42, homes could have gas appliances in new construction as long as the building met that better score of 42. They didn't do this for legal reasons, it was just a practicality thing. Getting a HERS score of 42 with gas appliances meant that walls had to be insulated to R37 or higher, which usually required five inches of closed-cell spray foam. It required blower door results around 0.5 air changes per hour, and it required an extremely well sealed, air tight design with extra air sealing measures taken on top of that. The insulation and air-sealing costs to get to that 42 was why a lot of builders moved toward all-electric designs because that 45 target was easier and cheaper to hit.

The February 2025 code change didn't create new permissions, it just got rid of an extra barrier. At a score of 52, the mixed-fuel path is actually possible for most ADU projects without taking extreme insulation measures that a score of 42 would require. That's the real significance of this change. Basically, having gas appliances was technically allowed but it was too expensive for most people to afford, and now with the 52 required score, most people are able to have to option.

Should You Go All-Electric or Mixed Fuel for Your ADU?

That question doesn't really have a universal answer. It really depends on three things. It depends on whether the person living in the ADU wants to cook with a gas stove, it depends on what kind of infrastructure your property already has, and it also depends on how it will affect your total construction cost to get to the better HERS score rating.

If the person living there doesn't really care about gas cooking, then going all-electric is easier because you only have to get a HERS 55 score. Also, you won't have to run a gas line, you avoid propane tank installation, and you have more flexibility on what kind of insulation you choose because a 55 is easier to achieve than a 52.

If the person really wants a gas stove, at least that is an affordable option now. The mixed-fuel path also means you can have a gas or propane hot water heater (which some homeowners prefer because the hot water fills up much faster) and gas heating if the property already has a gas line or propane setup. The ADU can even be fully gas-fueled for heating, hot water, and cooking, as long as measures are taken to get to that HERS 52 score.

One option worth knowing about. Under the lower HERS 55 all-electric score requirement, you can use a standard electric hot water tank instead of the more expensive heat pump hybrid water heater. A standard tank costs around $600 compared to $1,800 to $2,000 for the hybrid kind. In a small ADU with one bathroom and one occupant, a 30-gallon standard hot water heater can handle the demand without the noise, cold air output, and space requirements of a heat pump water heater. That cost savings for all-electric is something to think about when you're considering a gas stove.

Does the Relaxed Energy Code Mean I Can Skip the ERV?

No. This is the most common misunderstanding about the February 2025 code change. The HERS score target for ADUs changed, but that's not the same thing as ventilation requirements. All ADUs still require an ERV (Energy Recovery Ventilator) or HRV (Heat Recovery Ventilator) regardless of whether you go with all-electric or mixed fuel.

An ERV is a mechanical ventilation system that swaps out the stale indoor air for fresh outdoor air while recovering energy from the exhaust. An ERV holds on to about 50 percent of the moisture in the outgoing air, which helps prevent the dry, uncomfortable conditions air that most new england homes have in the winter. An HRV uses a metal core to condense and remove moisture, which works well in homes that also have a humidifier installed.

For most ADUs using a heat pump without a humidifier, the ERV is the way to go. It keeps the indoor humidity at a comfortable level all winter while still giving you the fresh air exchange the code requires. The code changed the energy performance target for ADUs, not the equipment requirements. Plan for the ERV in your budget regardless of fuel choice.

When Does the All-Electric Path Make More Sense?

We build both all-electric and mixed-fuel ADUs, and we don't have a preference of one over the other. The right choice depends on the family and the property. But there are situations where all-electric is clearly the better fit.

If your property doesn't already have a gas line or propane setup, running a new gas connection or installing a propane tank can add so much cost and time to the project that it might not be worth it for just one appliance. If the ADU occupant is comfortable with induction cooking (which a lot of people actually prefer once they try it), the all-electric path and a score of 55 is simpler to build and it doesn't require all the extra ventilation that gas appliances need. If your lot is tight and a propane tank creates setback or placement challenges, going all-electric is the easiest way to go.

We don't really care which way a customer wants to go, whether it's gas or electric. We just want to make sure that whatever you choose is right for your family's needs, your property's constraints, and your budget. If you walk into our office wanting a gas stove and we determine that the mixed-fuel path adds cost that does not make sense for your situation, we'll just tell you that.

Your Gas Stove Is Not a Dealbreaker. Your Energy Strategy Might Be.

The gas stove question has a clear answer: yes, it is allowed. The more important question is how the gas-versus-electric decision fits into your total energy strategy, your insulation choices, and your budget. That's the conversation you really need to have before you commit to a direction.